Process of agglomerating aerosols



1950 c. B. HORSLEY ETAL 2,535,679

PROCESS OF AGGLOMERATING AEROSOLS -Fi1ed Sept. 12, 1946 .2510 j rs.

Patented Dec. 26, 1950 PROCESS OF AGGLOMERATING AEROSOLS Caperton B.Horsley, Stamford, Conn., and Gordon C. Seavey, Arlington, Mass,assignors to Ultrasonic Corporation, Cambridge, Mass., a corporation ofMassachusetts Application September 12, 1946, Serial No. 696,628

1 Claim.

Our invention relates to the agglomeration of aerosols by sound waves.

In many industries valuable materials are lost because they are carriedoff in flue gases or other gas streams in the form of very finelydivided particles, so fine that they are suspended in the gas. Forexample, sign ficant quantities of carbon black are carried off anddissipated into the atmosphere together with their flue gases. In themanufacture of several kinds of soap products large quantities arecarried off and are not only lost for all practical purposes, butconstitute a serious nuisance in the surrounding neighborhood. There areother instances in which aerosols are undesirable. For example, inpetroleum refining there is sometimes formed a fog comprising smalldroplets of sulphuric acid dispersed in a gas.

We have discovered several important facts regarding the effects ofsound waves upon aerosols and have invented a process, based on ourdiscoveries, which may be followed to obtain the successfulagglomeration of aerosol particles by the application of sound waves.

It can be stated as a major premise that agglomeration of aerosolparticles may be brought about by increasing the collision expectancy.Inasmuch as it is not possible directly to affect the particle spacingor the particle size and shape,

the sound waves, if they are to be effective, must be applied in such away as to increase the velocity of each particle relative to otherparticles.

An important feature of the invention resides in improving the processof sonic agglomeration by continuously removing agglomerates from thetreating chamber and re-circulating them. Consequently there ismaintained in the treating chamber a desired range of particle sizes inthe aerosol undergoing treatment, since the agglomer tes maintained inthe treating chamber provide in eifect more targets for the smallerparticles to hit.

In the accompanying drawing there is shown schematically the arrangementof treating chamber, sound generator, and ducts by means of which ournovel process may satisfactorily be carried out.

As shown in the figure there is provided a tank or chamber l0 at the topof which is mounted a sound generator or siren 12. A sound wavegenerator capable of producing the required acoustic intensities on acommercial scale is described in the copending applicat on Ser. No.722,240, of Caperton B. Horsley and Richard E. Young, filed January 15,1947 as a continuation-in-part of an earlier application Ser. No.624,504 filed October 25, 1945, now abandoned. We have used such agenerator or a modification thereof in carrying out the process hereindisclosed. A conduit I4 is arranged to admit the aerosol to be treatedto the interior of the chamber l0 while an outlet duct I6 is providedadjacent the top of the chamber. In order to provide for there-circulation of some of the agglomerates leaving the chamber, there isprovided a by-pass duct or conduit l8 leading from the outlet duct Hi tothe inlet duct l4 adjacent its connection to the chamber I0. A small fan20 is provided in the duct It] in order to bleed off a desired portionof the agglomerates leaving the chamber and introduce them into theuntreated aerosol as it enters the treating chamber I 0. As statedabove, we have found it advantageous to provide means for maintainingsome of the agglomerated particles with the aerosol as it undergoestreatment rather than to permit the agglomerated particles to fall outimmediately. This in efiect increases the range of mass to drag ratios.By keeping agglomerated particles in the aerosol we provide. in efiect,more targets for the smaller particles to hit. In such a case thefrequency may be varied downward to correspond to the change in range ofmass to drag ratios. As shown in the figure, we withdraw agglomeratedparticles from one portion of the treating apparatus and put them backinto the aerosol at another place. The essence of the invention may besummed up broadly as recirculating agglomerated particles at a ratesuificient to maintain a desirable range of particle sizes in theaerosol undergoing treatment. The process is carried on continuously;that is to say, the aerosol is continuously introduced into the treatingarea, some of the agglomerated particles are removed and collected, andothers are recirculated to the treating area.

The process may be carried out at a fixed frequency lower than theoptimum for the range of mass to drag ratios in the untreated aerosolbut at or near the optimum frequency for the range of mass to dragratios present in the treating area and comprising the original aerosolmixed with agglomerated particles.

Having thus disclosed our invention what We claim as new and desire tosecure by Letters Patent of the United States is:

A process of agglomerating an aerosol, comprising passing the aerosolcontinuously through a chamber, subjecting the chamber and the aerosolto sound waves, withdrawing agglomerated particles from the aerosol asthe treatment 3 proceeds and continuously recirculating some of theagglomerated particles through the chamber together with untreatedaerosol in order to increase the collision expectancy of the particlesof the aerosol.

CAPERTON B. HORSLEY. GORDON C. SEAVEY.

REFERENCES CITED Number The following references are of record in the910 Number file of this patent:

UNITED STATES PATENTS Name Date Herbsman Dec. 2, 1930 Lewis June 30,1931 St. Clair Sept. 24, 1940 Houghton et a1. Oct. 8, 1940 Amy Nov. 3,1942 FOREIGN PATENTS Country 7 Date Great Britain Feb. 4, 1937

